U.S. patent number 6,053,432 [Application Number 09/368,447] was granted by the patent office on 2000-04-25 for fuel injector.
This patent grant is currently assigned to Lucas Industries, PLC. Invention is credited to John William Stevens.
United States Patent |
6,053,432 |
Stevens |
April 25, 2000 |
Fuel injector
Abstract
A fuel injector comprising a nozzle body, a bore provided in the
nozzle body within which a valve needle is slidable, the valve
needle and the bore being shaped to include a guide region where
the valve needle and the bore are of substantially identical
diameter, the engagement between the valve needle and the bore in
the guide region serving to guide the valve needle for sliding
movement within the bore, wherein the fuel injector includes a
collar extending around part of the nozzle body, the collar
engaging the nozzle body to restrict dilation of the bore in at
least part of the guide region.
Inventors: |
Stevens; John William
(Gillingham, GB) |
Assignee: |
Lucas Industries, PLC (London,
GB)
|
Family
ID: |
10838650 |
Appl.
No.: |
09/368,447 |
Filed: |
August 4, 1999 |
Foreign Application Priority Data
|
|
|
|
|
Sep 11, 1998 [GB] |
|
|
9819746 |
|
Current U.S.
Class: |
239/533.2;
239/533.11; 239/533.3; 239/583; 239/584 |
Current CPC
Class: |
F02M
61/12 (20130101); F02M 61/16 (20130101) |
Current International
Class: |
F02M
61/16 (20060101); F02M 61/12 (20060101); F02M
61/00 (20060101); F02M 061/00 () |
Field of
Search: |
;239/533.2,533.3,533.11,583,584,397.5,533.4,533.5,533.6,533.8,533.9,533.12,533.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kashnikow; Andres
Assistant Examiner: Evans; Robin O.
Attorney, Agent or Firm: Wells, St. John, Roberts, Gregory
& Matkins, P.S.
Claims
I claim:
1. A fuel injector comprising a nozzle body, a bore provided in
said nozzle body within which a valve needle is slidable, said
valve needle and said bore being shaped to include a guide region
where said valve needle and said bore are of substantially
identical diameter, engagement between said valve needle and said
bore in said guide region serving to guide said valve needle for
sliding movement within said bore, the fuel injector further
comprising a collar extending around part of said nozzle body, said
collar engaging said nozzle body to restrict dilation of said bore
in at least part of said guide region.
2. The fuel injector as claimed in claim 1, wherein said collar is
an interference fit on said nozzle body.
3. The fuel injector as claimed in claim 1, wherein said nozzle
body has parts of relatively smaller and relatively larger diameter
adjacent said guide region.
4. The fuel injector as claimed in claim 3, wherein said collar is
located only around said relatively smaller diameter part of said
nozzle body.
5. The fuel injector as claimed in claim 3, wherein said collar is
located around said relatively smaller diameter part of said nozzle
body and at least part of said relatively larger diameter part of
said nozzle body.
6. The fuel injector as claimed in claim 1, further comprising
clamping means for applying a clamping force to said fuel injector
to clamp said collar and said nozzle body in place.
7. The fuel injector as claimed in claim 6, wherein said clamping
means are a cap nut.
8. The fuel injector as claimed in claim 6, wherein said collar has
a surface of substantially frusto-conical form which engages a
surface of said clamping means, wherein said surface of said
clamping means is also of substantially conical form.
Description
This invention relates to a fuel injector for use in delivering
fuel at high pressure to a cylinder or combustion space of an
associated internal combustion engine.
During fuel injection it is common for the valve needle of a fuel
injector to be held in a position spaced by a small distance from a
seating, and when the needle is lifted by such a small distance it
is desirable to ensure that the needle and seating remain
concentric throughout the period during which the needle is lifted,
particularly where the lift of the needle is used to control the
injection rate, as otherwise the quality of the injection spray
formation can be impaired. In order to assist in ensuring that the
needle remains concentric with the seating, it is known to increase
the length of the part of the needle which contacts the surface of
the bore within which the needle is slidable to improve guidance of
the needle.
The fuel pressures at which such injectors operate are such that
the fuel pressure within the bore of the injector dilates the bore,
such dilation permitting lateral movement of the needle to occur.
Clearly, such movement results in the needle no longer remaining
concentric with the seating, and is undesirable.
It is an object of the invention to provide a fuel injector in
which this disadvantage is of reduced effect.
According to the present invention there is provided a fuel
injector comprising a nozzle body, a bore provided in the nozzle
body within which a valve needle is slidable, the valve needle and
the bore being shaped to include a guide region where the valve
needle and the bore are of substantially identical diameter, the
engagement between the valve needle and the bore in the guide
region serving to guide the valve needle for sliding movement
within the bore, and a collar extending around part of the nozzle
body, the collar engaging the nozzle body to restrict dilation of
the bore in at least part of the guide region.
The collar is conveniently an interference fit on the nozzle
body.
The provision of the collar acts, in effect, to increase the wall
thickness of the nozzle body and also applies a compressive load to
the nozzle body, these effects acting to improve the ability of the
nozzle body to withstand the application of fuel under high
pressure to the bore thereof without dilation of the bore occurring
to an unacceptably large extent.
The invention will further be described, by way of example, with
reference to the accompanying drawing which is a sectional view
illustrating part of a fuel injector in accordance with an
embodiment of the invention.
The accompanying drawing illustrates part of a fuel injector, the
drawing illustrating a nozzle body 10 within which a blind bore 11
of stepped form is provided, a valve needle 12 being reciprocable
within the bore 11. The needle 12 and bore 11 together define a
delivery chamber 13, the needle 12 including thrust surfaces 12a
exposed to the fuel pressure within the delivery chamber 13 such
that the application of fuel under high pressure to the delivery
chamber 13 applies a force to the needle 12 urging the needle 12 in
a direction away from a seating formed adjacent the blind end of
the bore to permit fuel to flow past the seating to one or more
outlet openings 14 located downstream of the seating.
The needle 12 includes a guide region 12b of diameter substantially
equal to the diameter of the adjacent part of the bore 11, the
guide region 12b of the needle 12 engaging the surface defining the
bore 11 and serving to guide the needle 12 for sliding movement
within the bore 11 whilst maintaining the needle 12 concentric
relative to the seating.
A part of the bore 11 adjacent the guide region 12b of the needle
12 is shaped to define an annular gallery 15 which communicates
with a drilling 16 forming part of a supply passage. The part of
the needle 12 between the annular gallery 15 and the delivery
chamber 13 is shaped to define flutes 12c whereby fuel is able to
flow from the annular gallery 15 to the delivery chamber 13, in
use.
The nozzle body 10 is shaped to define a region of relatively large
diameter and a region of smaller diameter, these regions being
interconnected at a shoulder 17 which is located at a level
substantially adjacent the annular gallery 15. It will be
appreciated that the relatively large diameter part of the nozzle
body 10 is able to withstand the application of fuel under
relatively high pressure to the bore 11, but the smaller diameter
part of the nozzle body 10 is less able to withstand the
application of fuel under high pressure to the bore 11 without
unacceptably high levels of dilation occurring, in use. Although
dilation of the bore 11 in the region of the delivery chamber 13 is
of relatively little concern, dilation of the parts of the bore 11
forming the guide region is undesirable as such dilation may result
in accurate guiding of the needle 12 being impaired, and hence in
the needle 12 no longer remaining concentric with the seating. In
order to restrict or avoid such dilation of the part of the bore 11
forming the guide region with which the guide region 12b of the
needle engages, a collar 18 is located around the nozzle body 10,
the collar 18 being an interference fit with the adjacent part of
the nozzle body 10 and applying a compressive force thereto, the
collar 18 being located and secured in position conveniently using
a thermal expansion technique. As the relatively large diameter
part of the nozzle body 10 is able to withstand dilation to a
greater extent than the smaller diameter part of the nozzle body
10, the collar 18 is only located around the smaller diameter part
of the nozzle body 10 adjacent the guide region. It will be
appreciated however, that if desired, the collar 18 could be
located around a greater part of the nozzle body.
In order to permit the nozzle body 10 and collar 18 to be secured
to the remainder of a fuel injector of any suitable type, a cap nut
19 is provided, the cap nut 19 engaging the collar 18 to clamp the
collar 18 and the nozzle body 10 to the remainder of the fuel
injector.
The injector may, for example, take the form of a fluid pressure
actuated injector, fuel being supplied to the supply passage of the
injector by an appropriate fuel pump. Alternatively, the injector
may comprise, for example, a common rail injector or a unit pump
injector.
As illustrated in the accompanying drawing, the collar 18 is
provided with an angled, frusto-conical surface 18a which is
engaged, in use, by a frusto-conical surface 19a forming part of
the cap nut 19 to apply the necessary clamping force, in use. The
use of such angled surfaces in applying the clamping force to the
injector results in the clamping force having a radial component
which assists in reducing dilation of the bore 11, in use.
The provision of a collar 18 is further advantageous in that it
permits a standard nozzle body 11 and needle 12 to be adapted for
use in a relatively wide variety of applications, effectively by
adjusting the axial length of the relatively large diameter part of
the nozzle body 10.
* * * * *